20 ANIMAL KESOURCES OF THE UNITED STATES 



60. ECHLNODERMATA— Continued. 



Injurious traits : 



Burrowers, (various echinoids.) 

 Destroyers of useful mollusks. 



61. CCELENTERATA. (Acalephs, polyps, &c.) 



Useful products: Coral, various species of polyps.) D. 17. 

 Injurious traits: Clog seines, weirs, and fishing-lines, (acalepbs.) 



XV. PROTOZOANS. 



62. RHIZOPODA. (Sponges and foraininifera.) 



Useful products : 



Food, "mountain meal," (foraininifera.) D. 1 

 Infusorial earths, (foraininifera.) D. 18. 

 Sponges, used in arts and manufactures. D. 26. 



